The semiconductor illumination is known as the fourth generation of illuminating source, and is gradually applied to the general illumination field. The power light emitting diode (power LED) is popular in the market because of its high brightness and high power. There are two types of conventional power LED brackets: a PLCC-type (plastic leaded chip carrier) bracket and a ceramic substrate bracket.
FIG. 1 shows a structural schematic view of a prior PLCC-type bracket. In the PLCC-type bracket, a plastic casing 01 having a reflection cavity covers a metal lead frame 02. The metal lead frame 02 includes a chip mounting portion 03 for carrying an LED chip 04, and an electrode pin 05. The chip mounting portion 03 forms an integral structure together with a positive electrode or a negative electrode. The PLCC-type bracket is particularly applicable to fields requiring a high light distribution and a high mounting density because of the reflection cavity and compact structure of the PLCC-type bracket. A high power LED may generate high heat energy in operation, thus it needs to take some technical means to help to dissipate the generated heat energy. Otherwise, the lifetime and light emitting effect of the high power LED will be affected. In a typical packaging structure of the PLCC-type bracket for the high power LED, the plastic casing having the reflection cavity not only covers the metal lead frame, but also covers a heat sink provided at the bottom of an LED chip and exposed outside the bracket. The heat sink generally employs a metal material having a good heat dissipation effect, such as copper, to facilitate the dissipation of the high heat energy generated in the operation of the LED. The PLCC-type high power LED is one of the most commonly used high power LED packaging structures because of the good heat dissipation effect thereof.
Another conventional power LED bracket is the ceramic substrate. A typical packaging structure of the ceramic substrate is shown in FIG. 2. A substrate 06 for carrying an LED chip, and a reflection cavity 07 arranged on the substrate 06 employ a ceramic material. As to a power LED device, at least one through hole 08 is provided in a chip mounting portion of the substrate 06, with a heat conductive material being filled in the through hole 08 for increasing the heat dissipation effect, to meet heat dissipation requirement of the high power LED device. Since the ceramic substrate has good insulating property and heat dissipating property, the ceramic substrate is widely applied to the high power LED field, and occupies the whole high power LED market together with the PLCC-type bracket.
However, the PLCC-type bracket and the ceramic substrate have some disadvantages. As for the PLCC-type bracket, manufacture processes thereof are complicated and require a high precision. Many relevant patent applications have been developed, however, key technologies of these patent applications are still grasped by foreign enterprises, and these technologies are relatively mature and have limited rooms for improvement. Especially for the PLCC-type bracket for a power LED, a heat sink is further needed to improve heat dissipation of the bracket. Thus, it needs to further provide a counter bore and mount the heat sink in the counter bore, which causes the structure of the PLCC-type bracket for a power LED more complicated, and thus the bracket packaging process is more complicated. At the same time, the PLCC-type high power LED has a large volume, the packaging structure thereof cannot be applied to a reflow soldering process, is not applicable to a full-automatic and batch testing and taping process and is inconvenient for a batch soldering and mounting of the down-stream products, and is particularly inconvenient for the subsequent surface mounted processes of the manufacture of the LED product. Therefore, the prior PLCC-type bracket has a complicated structure, a relatively complicated manufacture process and a relatively high production cost, which limits the subsequent manufacture processes of the product, increases the production cost of the subsequent LED products, reduces the production efficiency, and accordingly limit the application range of the PLCC-type bracket power LED.
The ceramic substrate may overcome the main disadvantages of the PLCC-type bracket, however, the ceramic substrate has some common problems, for example, manufacture processes of the ceramic substrate are difficult, cost of the ceramic substrate is high, and material of the ceramic substrate is fragile, which are key factors that restrain the ceramic substrate from fully substituting the PLCC-type bracket.
Based on the above description, there is a need to provide an LED bracket structure and a manufacture process thereof, the LED bracket structure has a simple manufacture process, a good light emitting effect, a good heat dissipation effect and a low production cost, and compared with the above PLCC-type bracket and ceramic substrate, the LED bracket structure can overcome the above technical drawbacks of the prior PLCC-type bracket and ceramic substrate. In the prior technical improvements, the person skilled in the art has already made attempts to improve the manufacture material and the manufacture process. However, these attempts can not properly solve or overcome the above technical drawbacks.
Before making the present application, applicants of the present application filed a patent application (China Patent Application No. 201010165442.3) titled “METHOD FOR MANUFACTURING A SURFACE MOUNTED POWER LED BRACKET AND THE SURFACE MOUNTED POWER LED BRACKET”, which provides a method for manufacturing a surface mounted power LED bracket by employing a single-sided copper coated circuit board and a metal sheet, and the bracket product. This technical solution has such advantages as having a simple manufacture method, a low cost and a good heat dissipation effect. This technical solution can overcome drawbacks of the commonly used PLCC-type bracket and ceramic substrate for the power LED, and has a potential of occupying the power LED bracket market. However, it is discovered in the further research that, since the metal sheet is connected to the single-sided copper coated circuit board only via an adhesive film, there may be a gap between the metal sheet and the edge of the bottom of a through hole in the single-sided copper coated circuit board, which may cause the LED bracket hard to pass reliability tests such as the “red ink test”, and thus affect the reliability of the power LED bracket. Further, since the bottom of the through hole and the metal sheet are not closely connected, the bottom surface of the chip mounting portion may not be continuously smooth, which may reduce the light reflection efficiency of the LED chip.
In light of the above technical drawbacks, the present application provides a new technical solution to solve the above technical drawbacks. The present application can overcome the technical prejudice, as is commonly accepted by the person skilled in the art, that an ordinary insulating board, such as a PCB board, is not applicable to be employed as a packaging material for the power LED. Meanwhile, the present application can solve the problem that there may be a gap between the metal sheet and the edge of the bottom of the through hole when using a single-sided copper coated circuit substrate as a substrate, and provides a method for manufacturing a power LED bracket and the power LED bracket with a simple process, a low cost, a high reliability, a wide application range, a high heat dissipation property and a high light reflection efficiency.